High-frequency transformer having coaxial leads



April 24, 1951 F. H. GUSDORF ET AL 2,550,244

HIGH-FREQUENCY TRANSFORMER HAVING COAXIAL LEADS Filed July 15, 1946 159512621X HZWZZRUK 605170121 fiWflZ/DADBMAN WUVIHEREN INVENTORS ATTORNEY ,the magnetic circuit pertaining thereto.

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Patented Apr. 24, 1951 HIGH-FREQUENCY TRANSFORMER HAVING COAXIAL LEADS Frederik Hendrik Gusdorf and Ewoud Adriaan van Ijzeren, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 13, 1946, Serial No. 683,562 In the Netherlands October 27, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires October 27, 1963 Claims.

The present invention relates to high-frequency inductive coupling devices.

. In'high-frequency techniques use is very frequently made of combinations of two or more than two high-frequency coil systems housed in a casing, for example, in a metal box. By a coil system is meant a coil, as the case may be, with Such combinations are used inter alia as high-frequency transformers. It is a well-known requirement thatthe casing should be as small as possible and more particularly, should have the smallest possible diameter, in order to save space in the apparatus in which the combination is to be mounted. This entails difiiculties when providing the current supply wires of the systems within the casing. If two systems are arranged inline with one another in a casing and if the current supply contacts are provided in the usual manner at one end of this casing, the current supply wires of the one system must necessarily be led past the other system, in which event a harmful capacitative coupling is unavoidable.

This coupling can only be avoided by leading the current supply wires of each system to the nearest end of the casing. -This solution can, however, only be used if not more than two systems are housed in the casing. 'A further drawback resides in that the casing must be left open at both ends,

which'gives rise to the production of a comparatively strong leakage field outside the casing.

The object of this invention is to avoid the above-mentioned drawbacks. According to the invention, at least one of the current supply wires of one of the systems is led past one or more of the other systems by means of a condenser of which one electrode, at one end, is connected to the system and, atthe other end, is taken out of the combination whereas the other electrode is earthed and forms a screen between the first electrode and the other coil system or The condenser may have the shape of a wire and may have a diameter which preferably amounts to 2 mm. at the most. By a wireshaped condenser is meant hereinafter a condenser consisting of a wire-shaped core and a layer of insulating material narrowly surrounded by a conductive sheath. I

This condenser is preferably manufactured in the manner known per. se for wires, by jointly drawing and/or swaging'a conductive core and sheath separated by insulatin material.

If such a combination is arranged in an apparatusgthe circuit-arrangement and the dimensions of the condenser should preferably be material, for example, of artificial resin.

chosen in such manner that the condenser and the appurtenant coil system jointly form a tuned circuit.

In order that the invention may be clearly understood and readily carried into effect, it will now be explained more fully with reference to the accompanying drawing, in which one form of construction is represented by way of example.

Fig. 1 is an axial section through a combination according to the invention.

Fig. 2 is a section on the line II-II in Fig. 1.

Figs. 3 and 4 represent the circuit-arrangement of part of an apparatus, viz. an intermediatefrequency amplifier, in which use is made of the combination according to the invention.

Fig. 5 shows, in section, a wire-shapedcondenser as included in the combination.

The combination according to Figs. 1 and 2 comprises two coil systems. Each of these systems comprises a coil or winding 1 provided on a core 2 of high-frequency iron. The cores 2 are coaxially surrounded by tubular sheaths 3 which also consist of high-frequency iron. By highfrequency iron is meant a magnetic material which, even in a field of high frequency, only causes low losses. It may consist of very finely divided iron and a binder. The cores 2 are hollow; in the hollow interior is provided and adjustable pin 4 of high-frequency iron, which is fastened, for example, by means of cement. The cores and sheaths are supported with respect to one another by flanged bodies 5 consisting of non-magnetic and electrically non-conductive The arrangement of the cores and sheaths, the mounting of thepins and the arrangement of the systems opposite one another form the subjectmatter of the copending application No. 661,524, filed April 12, 1946, now Patent No. 2,544,152, issued March 6, 1951.

The two systems are arranged in a cylinder 6 which closely surrounds the various components. When mounting the combination the connections taken out of the apparatus are connected to soldering tags 1 which are fixed in the lower body 5.

These soldering tags are connected on the other hand to the ends of the coils I. It is evident that for this purpose the ends of the upper coil must be taken past the lower coil system and that they thus experience a fairly strong capacitative coupling with the lower coil. This coupling may be avoided by using a condenser 8, shown separately in Fig. 5, of which the one electrode is connected, at one end, to one of the ends of the upper coil and, at the other end, to a soldering tag, whereas the other electrode is earthed and forms a screen between the first electrode and the lower coil.

The first electrode may be formed as a wire and the second as a metal strip. In the example shown use is made of a wire-shaped condenser, i. e. a condenser obtained by drawing and/or swaging a copper core jointly With a copper casing separated from the core by an insulating material which preferably causes low losses, for example, polystyrol or titanium di- 1 oxide, until a wire of great length and of small diameter is obtained. The diameter of such a condenser may be less than 2 mm.

In the combination in question use is made of two condensers of this kind. At the lower end their sheaths and cores are connected to the soldering tags 7. At the upper end the sheaths are soldered to flanged bushes 9, four of them being provided in the upper body 5. The ends. of the upper coil l are taken to two of these bushes. One of these two bushes is connected to a bush to which the sheath of a condenser is secured; the core ii] of this condenser is taken to the other bush (see also Fig. 2). The core and the sheath of the other condenser is connected at the lower end to the ends of the other coil.

The condensers contribute to keep together the various components of the coil systems, even before they are mounted in the cylinder 5. It

is thus possible to carry out preliminary measurements on the combination even in'this stage.

The diameter of this combination is very small; it need not be more than 16 mm.

The manner in which such a combination may be used is shown in Figs. 3 and 4.

Fig. 3 shows the usual circuit-arrangement of an intermediate-frequency amplifier, in which the coupling between two tubes Ii and i2 is brought about by two tuned circuits, each of which consists of a condenser 53 and a coil Hi. The coils are magnetically coupled. Those ends of the coils which are not earthed with respect to high frequencies should be screened, as is shown by dotted lines. This requirement also applies, of course, to those supply wires of the condensers which are connected to these ends.

If these condensers are constructed in the manner according to the invention and, besides, if care is taken to ensure that they have such a capacity that, jointly with the appurtenant coil system, they form a tuned circuit, we obtain the diagram according to Fig. 4. Here we find again the two wire-shaped condensers 8 which are connected so as to form, jointly with the coils l, tuned circuits. In the right-hand condenser of Fig. 4 the connections of the upper coil are taken past the lower one.

What we claim is:

1. A high-frequency coupling device comprising a tubular casing, a pair of inductors mounted within said casing at spaced longitudinal positions therein, connectors for said inductors mounted at one end of said casing, leadsdisposed within said casing and extending from said connectors to the respective terminals of said inductors, the leads extending from the inductor remote from said connectors being constituted by a first coaxial cable having an inner conductor surrounded by an outer conductor and separated therefrom by a dielectric substance, said outer conductor of said first cable electrostatically shielding the inner conductor thereof from the inductor adjacent said connectors, said first cable having dimensions defining a capacitance to form a tuned circuit with said remotely disposed inductor, and a second coaxial cable longitudinallyarranged within said casing, said second cable having two conductors connected at one end to the connectors for the inductor adjacent thereto and having dimensions defining a capacitance to form a resonant circuit with said adjacently disposed inductor.

2. Ahigh-frequency coupling device comprising a pair of inductors each including a cylindrical magnetic shell, a magnetic core coaxially disposed within said shell, a non-magnetic disc supporting said core and enclosing one end of said shell and a coil surrounding said core within said shell, an open-ended cylindrical spacer, the shells of said inductors being secured at their open ends to either end of said spacer to form a tube of uniform diameter, a casing surrounding said tube, connectors inserted in the disc of one of said inductors, first and second coaxial cables extending between and secured to the discs of said inductors, each cable including an inner conductor, an outer conductor and dielectric material interposed therebetween, the first cable being connected between the terminals of the other of said inductors and respective connectors, and leads connecting the terminals of said one of said inductors to respective connectors, the second cable being connected at one end to the respective connectors for said one of said inductors, said cables being dimensioned to provide predetermined values of capacitance.

3. A high-frequency coupling device comprising a casing, first and second inductors mounted within said casing at spaced longitudinal positions therein, a plurality of contacts for said inductors mounted at the end of said casing adjacent said first inductor, means connecting said first inductor to the contacts therefor, and a wire-shaped condenser disposed longitudinally within said casing and constituted by an inner conductor surrounded by an outer conductor, said inner and outer conductors connecting said second inductor to the contacts therefor, said condenser having a value'forming a resonant circuit with said second inductor, said outer conductor of said condenser shielding said'inner conductor from said first inductor. 1

4. A device, as set forth in "claim 3, wherein said condenser is constituted by a coaxial cable having an inner conductor surrounded by an outer conductor and separated therefrom by a dielectric substance.

5. A device, as set forth in claim 3, further including a secondwire-shapedcondenser longitudinally disposed within said casing and constituted by an inner conductor surrounded by an outer conductor, said second condenser being connected to the contacts for said first inductor and having a value forming a resonant circuit with said first inductor, 1 v V FREDERI-K HENDRI'K GUSDORF. EWOUD ADRIAAN VAN IJZEREN.

REFERENCES CITED The following references are. of 'recordin the file of this patent:

UNITED STATES PATENTS 

